Multiple discharge lamp circuit



March 30, 1948.

E. LEMMERS MULTIPLE DISCHARGE LAMP CIRCUIT Filed July 11, 1945 2Sheets$heet 2 [N VE/V TERI EUGENE L EMMEHS 5 W H/s AT TUNA/E Y PatentedMar. 30, 1948 MULTIPLE DISCHARGE LAIdP CIRCUIT Eugene Lemmers, ClevelandHeights, Ohio, assignor to General Electric Company, a corporation ofNew York Application July 11, 1945, Serial No. 604,339

2 Claims. 1

This invention relates to electric discharge devices or lamps and theircircuits, and is especially concerned with the starting and operation ofa plurality of such devices in parallel. The invention. aims at assuringthe starting and stable operation of all the devices, and at keepingdown the circuit losses during operation, after starting. A furtheradvantage of the invention is that it allows of controlling a bank oflamps by one single switch. The invention is especially useful forfluorescent lamps of the usual low-pressure positive column type, andparticularly (though not exclusively) in railway train lighting.

Various other features and advantages of the invention will appear fromthe description of species and forms of embodiment, and from thedrawings.

In the drawings, Fig. 1 shows a simple circuit arrangement embodying theinvention; Fig. 2 illustrates the adaptation of the ircuits to lampswhose electrodes are preheated for starting; and Fig. 3 illustrates theadaptation of the arrangement to lead and lag circuits.

Fig. 1 shows a plurality of low pressure positive column discharge lampsI, I each consisting of an envelope tube equipped with widely spacedcooperating electrodes 2, 2 in its opposite ends. Either or each of theelectrodes 2, 2 may be a thermionic activated cathode embodying anelectric heater for bringing it to a temperature of electron emissionbefore the discharge between the electrodes is initiated. For instance,the electrodes 2, 2 may consist of tungsten filament wires, in coil orcoiled coil form charged or coated with activating alkaline earthoxides, such as a miX- ture including barium and strontium oxides. Theenvelope I may contain an atmosphere of gas or vapor or both at lowpressure: e. g., an inert rare starting gas, like argon at 2 to 6 mm. ofmercury, and a suppl of mercury that is indicated by a droplet 3. Also,an internal coating of luminescent material or phosphor l excitable bythe radiation from the discharge is indicated on the envelope walls.Since the system illustrated in Fig. 1 has no provisions for preheatingthe oathode(s) 2 before discharge is initiated, these cathode(s) shouldbe of a type adapted for cold or instant starting, such as thatdisclosed in U. S. Patent No. 2,306,925 to John O. Aicher.

As shown, the discharge lamps I, I are connected in parallel circuits 5,5 across a main discharge circuit 6 which may be energized from anysuitable A. C. source-such as a 110 volt 60 cycle lighting circuit. Twosuch parallel lamp circuits 5 are here represented; but the number isgenerally unimportant. Each lamp circuit 5 includes the usual inductiveballast or reactor I, and a manual switch 8 for controlling energize.-tion of the whole circuit 6 is also shown. A starting circuit 9 isprovided for connection across the circuit 6 in parallel with each lampI, and includes an additional auxiliary inductive ballast or choke Itfor starting purposes. The several circuits 9 are shown as connected atcorresponding ends to a common circuit lead II which may be connected toa corresponding side of the circuit 5 by means of a switch I2 of eithermanual or automatic type. The other ends of the several circuits 9 areconnected to the other side of the circuit 6, preferably throughportions of the circuits 5 that include the corresponding ballasts I,rather than directly and independently.

The discharge circuit 6 being in the present instance a lagging powerfactor circuit, a capacitor or condenser I3 is shown connected in eachstarting ircuit 9 in series with its inductive ballast ID. In the caseof a discharge circuit 6 with a leading power factor, however, thecapacitor or condenser I3 would be connected in the lamp circuit 5itself instead of in the corresponding starting circuit 9, ashereinafter more fully explained and illustrated. The values of the lampcircuit inductances I (and of the capacitors I3, when included in thecircuits 5) are so chosen that during operation the desired dischargecurrent and a suitable voltage less than the supply voltage on thecircuits 5 are maintained across the electrode gap 2, 2 of eachdischarge device I. The values of the starting circuit inductances I0and of the capacitors I3 (when the latter are in the circuits 9, as hereshown) are so chosen that the total circuit which in effect shunts eachlamp I across the line 6 (when the switch I2 is closed during starting)is a resonant circuit which produces across the electrode gap 2, 2 avoltage exceeding the supply voltage in the circuit 6 and the breakdownvoltage of the lamp I. With the connection shown in Fig. 1, each suchresonant circuit includes the inductance I as well as the inductance IIIand the capacitor I3, and the values of the last two are correlated withthat of the inductance I to produce the desired resonance and thedesired starting voltage on the lamp. The same is also the case when thecapacitor I3 is in the circuit 5, as above mentioned.

It will be seen that with the system as shown in Fig. 1, the connectionfrom each lamp I to its neighbor via their circuits 9, 9 and theintercom necting-portion of lead II includes a large impedance: via, twocapacitors [3, I3 and two chokes I 0, I9. Considerable impedance in thisconnection 9, I I, 9 between corresponding ends of adjacent lamps I, Iis an essential condition for the stability of the system during theperiod when switch I 2 is closed, in order to insure proper starting andcontinued operation of both lamps. If, on the contrary, the impedance ofthis connection is inadequate, only one lamp I will start; or if bothstart, one will presently drop out. The presence of high or substantialimpedance in the starting circuits 9, 9, serves to minimize circulatingcurrents between these circuits which would otherwise tend to flow byvirtue of the common connection and dissimilarities in circuit constantsand lamp operating characteristics. If such current limiting impedanceis not affording, the circulating currents assume such proportions thatan initially started lamp may undergo volt age variations at itsterminals which prevent the maintenance of an arc dischargetherethrough.

When the circuits 5 and 9 are first energized by closing the controlswitch 8, the current in each combined circuit 5, 9 and the Q andresonance of this circuit sufiice to give a voltage exceeding thebreak-down voltage of the corresponding lamp I, so that the dischargestarts and becomes established in the lamp. The discharge onceestablished, the efiective impedance of the lamp I becomes less thanthat of the circuit 9, resulting in a reduction of the current in thiscircuit. As soon as the discharges become established, or directlyafter, the switch I 2 is opened (either manually or by its owntime-delay action), so that the starting circuits 9 no longer carrycurrent or consume power. The losses due to the ballasts 1 duringoperation are very moderate, and only what is characteristic offluorescent lamp circuits generally.

Fig. 2 illustrates the adaptation of the system shown in Fig. 1 to hotcathode resonant circuits for a bank of lamps I whose cathodes 2, 2 arepreheated by passage of current before discharge is initiated. Theprincipal difierence is the provision of a heating circuit I4 for eachcathode coil or heater 2 of each lamp I, this circuit I4 being energizedfrom the corresponding starting circuit 9, and as here shown including aportion of the circuit" 5. For this purpose may be used a transformerwhose primary is the winding of the auxiliary starting inductance I and.Whose secondary is a winding I5 connected in the circuit I4 andassociated with the winding I9 and its core. With this arrangement, thevalues of the inductance Ill and capacitor I3 (when the latter is alsoin the starting circuit 9) may be so chosen as to produce a voltageacross the electrode gap 2, 2 that is lower than in the Fig. 1 system,and only suffices to initiate the discharge after the atmosphere in thelamp I has been ionized by a preliminary discharge along each cathodecoil 2, as is usual in the hot-starting of ordinary fluorescent tubes.It will be observed that opening of the switch I2 after startingsubstantially deenergizes the cathode heating circuits I4, I4, as wellas the starting circuit 9.

As another difference from Fig. I that is illustrated in Fig. 2, it maybe mentioned that the windings of the ballasts I, I0 foreach lamp I' arewound on a common core, which also carries the secondaries 15, I5.

For the convenience of those wishing'to use my invention, I will nowgive illustrative values of circuit constants suitable for an ordinarycommercial 15 watt positive col imn fluorescent lamp of usual 18 inchtube length and 1 inch diameter;

4 but these are not to be understood as defining or limiting theinvention in its broader aspects.

In the case of the lag circuits of Fig. 2, the inductance I may be woundto give a 108 volt drop on a 60 cycle A. C. current of 0.33 amp. R. M.S., with ,a D. C. resistance of 15 ohms or less, and the inductance I0may be wound to give a 92 volt drop on a 60 cycle A. C. current of 0.33amp. R. M. S., with a D. C. resistance of'36 ohms or less. The capacitorI3 may be a two microfarad condenser. Accordingly, the total reactanceI3, I3, I9, III. in the connection 9,. II,"9 between adjacent lamps I, Iamounts to as much as 3200 ohms, as against some 1400 ohms which I havefound necessary for stabilization as explained above. The cathode coils2, 2 of each lamp I are assumed to. be the usual coiled coils of the 15watt lamp above mentioned, each comprising an active length of 252 mm.of 2.54 mil tungsten wire.

Fig. 3 illustrates the adaptation of the system shown in Fig. 2 to abank of lamps I whose circuits 5 are lag and lead circuits arranged inalternation; Accordingly, the first and third circuits are essentiallylike those shown in Fig. 2, with the capacitors I3 in the startingcircuits'9, while the second and fourth circuits have their capacitorsI3 in the lamp circuits 5, between each lamp I and its ballast I, asalready referred to in connection with Fig.1. Fig. 3 also differs fromFig. 2 in showing the ballasts l as entirely separate from the ballastsI9, instead of having their windings on the same core as said ballastI9. While in Fig. 3 the connection from each lamp I to ts neighbor viatheir circuits 9, 9, and the lead I I includes only the impedancerepresented by one capacitor I3 and two chokes I6, I9-instead of twocapacitors I3, I3 and two chokes I9, I9, as in Figs. 1 and 2thisimpedance I3, I9, I 9 is nevertheless very considerable, and sufficientto stabilize the action of the system during the period when switch I2is closed, as already explained in connection with Fig. 1.

In Figs. 2 and 3, various parts and features are marked with the samereference characters as their counterparts in Figs. 1 and 2, as a meansof dispensing with repetitive description.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination, an alternating. current supply circuit, a dischargecircuit and a plurality of electrical discharge lamps connected acrossthe same in parallel circuits each including inductance, of resonantcircuits connected in parallel to oneside of said discharge circuit andeach including inductance and capacitance in series; and means includinga switch for connecting said resonanti circuits to the other side of thedischarge circuit during starting, and for disconnecting these resonantcircuits from said other side of the discharge circuit during subsequentlamp operation; the aggregate impedance represented by' the inductanceand capacitance in the connection between adjacent lamps via said meansbeing sufiicient to assure starting of said lamps and also stableoperation of all the lamps by minimizing circulating currents among thestarting circuits. 1 r

2. The. combination, an alternating current supply circuit, adischarge'circuit and a plurality of electricdischargelamps connectedacross the said discharge circuit through the inductive porside of thedischarge circuit during starting, and 10 for disconnecting thesecombined circuits from said other side of the discharge circuit duringsubsequent lamp operation; the aggregate impedance represented by theinductance and capacitance in the connection between adjacent lamps viasaid coimnon lead being sufiicient to assure starting of said lamps andalso stable operation of all the lamps by minimizing circulatingcurrents among the starting circuits.

EUGENE LEMMERS.

REFERENCES CITED I The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,922,984 Soundy Aug. 15, 19331,984,489 Mutsaers Dec. 18, 1934 15 2,046,980 Van Wijk July 7, 19362,170,448 Edwards Aug. 22, 1939

